Eritrea/Yemen - Sovereignty and Maritime Delimitation in the Red Sea

The State of Eritrea and the Republic of Yemen both claimed sovereignty over a group of islands in the Red Sea and disagreed as to the location of their maritime boundary. The Arbitration Agreement, between the Parties dated October 3, 1996, required the Tribunal to rule on these two issues in separate stages.

In its award in the first stage dated October 9, 1998, the Tribunal found that neither Party made a significantly more convincing case for ownership of any of the islands based on ancient title, as argued by Yemen, or a succession of title, as asserted by Eritrea. After reviewing the evidence, the Tribunal decided that Eritrea had sovereignty over the Mohabbakhs, the Haycocks, and the South West Rocks, because of their proximity to the Eritrean mainland. The Tribunal found Yemen to be sovereign over the Zubayr group because of its installation and maintenance of lighthouses on certain of these islands and the inclusion of the Zubayr group in two oil production agreements contracted by Yemen with private firms. Yemen was also found to be sovereign over the Zuqar-Hanish group on the balance of the evidence regarding the exercise of the functions of state authority.

In the second award dated December 17, 1999, the Tribunal effected its delimitation of the maritime boundary between Eritrea and Yemen. While Eritrea was not a party to the United Nations Convention on the Law of the Sea 1982 (“UNCLOS”), the Tribunal found that many of the relevant elements of customary international law were incorporated into the corresponding provisions of UNCLOS and that Eritrea had accepted the application of these provisions by reference to UNCLOS in the Arbitration Agreement.

The Tribunal ruled that the international maritime boundary between the Parties “shall be a single all-purpose boundary” that “should, as far practicable, be a median line between the opposite mainland coastlines.” This solution was not only in accord with precedent but was also familiar to both Parties and reflected by offshore petroleum agreements entered into by Yemen, Eritrea, and Ethiopia. The Tribunal then calculated the boundary line resulting from the application of these principles and set out the geographical coordinates of the international maritime boundary in the dispositif of the award.